Density functional study of the magnetic properties of Bi4Mn clusters: Discrepancy between theory and experiment.

We have performed collinear and noncollinear calculations on neutral Bi4Mn and collinear ones on ionized Bi4Mn with charges +1 and -1 to find out why theoretical calculations will not predict the magnetic state found in the experiment. We have used the density functional theory to find a fit between the theoretical prediction of the magnetic moment and the experimental value. Our calculations have consisted in a structural search of local energy minima, and the lowest energy magnetic state for each resulting isomer. The geometry optimization found three local minima whose fundamental state is the doublet spin state. These isomers could not be found in previous theoretical works, but they are higher in energy than the lowest-lying isomer by ≈1.75 eV. This magnetic state could help understand the experiment. Calculations of noncollinear magnetic states for the Bi4Mn do not lower the total magnetic moment. We conclude arguing how the three isomers with doublet state could actually be the ones measured in the experiment. [ABSTRACT FROM AUTHOR]